Safety device for switches



Oct.. 15,v 1929. w, Q HARTWIG SAFETY DEVICE FOR SWITCHES Filed April 12, 1926 nN RN WN. QN

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Patented Oct. 15, 1929 UNITED STATES PATENT OFFICE WILLIAM G. HARTWIG, OF CHICAGO, ILLINOIS, ASSIGNOR TO RAILWAY UTILITY COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS Application filed April 12,

My invention relates to that type of switch used for controlling currents of some magnitude, as for example, for motor-driven machines, in which the switch proper is enclosed in a casing and there is provided a socket and plug for conveniently connecting the switch in the circuit in which it is employed and disconnecting it therefrom. In devices of this character, as is well-known, serious results may follow and frequently have resulted from the pulling or insertion of the plug while the switch is in the closed position. Prior to my invention means has been devised for so interlocking the switch and the plug that the latter cannot be withdrawn except when the switch is in the open position. My invention relates to an improvement in means of this character and has for its object to provide a simple and reliable construction adapted to switches of this general character, notwithstanding speciie diiferences therein and which may be readily incorporated in such constructions at a minimum of expense. I have described herein and shown in the accompanying drawings a preferred form of my invention as applied to such a switch of known type. It is to be understood, however, that the specific disclosure is for the purpose of eXempliica-tion only and that the scope of 3o the invention is defined in the following claims in which I have endeavored to distinguish it from the prior art so far as known to me without, howevergrclinquishing or abandoning any portion or feature thereof. In the drawings accompanying and forniing a partof this specification, Fig. 1 is a vertical section through the center of such a switch to which my invention has been applied, and Fig. 2 a plan view partly in section of so lnuch thereof as will aid in understanding the nature of my improvement.

In the embodiment of the invention shown in the drawing, the switch proper and its enclosing casing are of known construction, the

casing comprising a main casting 3 within which the base 4 for the switch is mounted, and a. cover plate 5 in` which is journalled the hand operated means 6 for throwing the switch.

5o In the form of switch chosen for illustra- 1926. Serial No. 101,487.

tion of the invention there are two pairs of stationary contacts 7 8 with which cooperate the pivoted oscillating contact or bridging members 9-9.

The movable contacts are each carried between a pair of insulating blocks 10 and 11 mounted on a stub 12 which is journalled at 13 in one ofthe sides of the U-shapcd bracket 14. A U-shaped yoke 15 is secured to the two shafts 12 and the pairs of insulating blocks 10 and 11 so as to form therewith a movable contact member. A bell crank lever 16 is pivoted at 1T between the side pieces 14 of the U-Shaped bracket, and the arm 16a of said lever is perforated to receive a rod or pin 18 which. at its other end, extends through a hole 19 in the cross-member 15a of the pivoted yoke 15. A spring 2O surrounds said pin or rod and is compressed between the arm 16Zt of the lever 16 and the cross-member 15a of the pivoted yoke. The pivoted yoke is limited in its clockwise movement (as seen in Fig. 1) by engaging the edge 21 of the U-shaped bracket and its movement in the other direction is arrested by contact with the edge 22 of said U-shaped bracket. The arm 16b of the bell crank lever 16 may be swung from the full line position shown in Fig. 1 to the dotted line position, by the. hand operated device 6. Manifestly with the parts in the full line position of Fig. 1, the closed position of the switch, the pressure of the spring 20 holds the yoke 15 in contact with thestop surfaces 21. "hen the bell crank lever 16 is swung towards the dotted line position and after the spring 20-is carried past the pivotal point 12 of the yoke 15 the pressure of the spring throws the yoke to the dotted line position. the open position of the switch. At 23 are shown insulating shields.V

As `heretofore stated the switch per se is old and is not claimed herein except 1n com-l bination with the interlocking device hereinafter described. The switch box is provided with a sleeve or socket 25 for the insertion of the plug 26. The plug and socket are per se `spectively. The terminals 28 may be con- -formed with trunnions 34 which trunnions,.

when the `device is assembled,` rest loosely within the transverse channel 32. o The left hand end of the latch, as seen in Fig. 1 is oii' y set or hooked as at 36 to enter a notch or perforation 37 in the shell of the plug. The other arm 38 of the latch is so bent that when it is engaged by the operating member or yoke 15 of the switch it is thrown into the full line position in which the hook 36 enters the opening37 in the plug shell. Thus when the switch is in the closed position shown the plug can neither be inserted in nor withdrawn from the socket, being prevented therefrom by the latch. When, however, the switch is in the open position shown in dotted lines in Fig. 1, the latch is ,free tomove back into the channel or groove in the interior of the socket. A spring plateAO is formed with a finger 41 which extends over the top of the latch and tends to restore the latter to the dotted line position. The spring plate is screwed to the face of the socket at 42 and extends over the cross-channel 32 at 43,`thus serving also to retain the trunnions of the latch in position in the cross-channel. i

The switch is operated and the plug inserted and withdrawn in the usual manner,

but when the switch is in closed position, the

plug can neither be inserted nor withdrawn thus preventing and eliminating danger of firel and injury which otherwise might resultl from the closing or opening of the circuit by the insertion or withdrawal of the plug.

Manifestly when the switch is in the closed position shown, the pivoted latch is held inimovably in the full line position. If'the plug is already in place, it cannot be withdrawn.v Or if it be attempted to insert the plug, the end of the latter will engage the lug on the. latch and be prevented from being inserted to close the circuit. When, however, vthe switch is in the open, or dotted line position, the spring retiac-ts the latch to the dotted line position and the or withdrawn.

I claim:

In a device of the cla-ss described, a casing having a switch therein, said switch comprising a member movablepfrom open to closed :`position, a plug socket on the casing having a longitudinal groove and having a. transverse groove upon its inner face, a latch having trunnions 1n said transverse grooveand the engaging' end of which latch extends into plug may be freely inserted said longitudinal groove in the socket, said latch also eXtJending into the path of movement of the movable member of the switch and locked by the latter in plug engagieng position when the switch is closed, and a spring plate extending over the transverse groove and holding the trunnions of the latch therein and comprising also a spring finger tending to press the latch into non-engaging position.

In testimony whereof, I have subscribed my name.

WILLIAM G. HARTWIG.

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